During optical analysis of a test sample, the sample is often held in a sample chamber of a cuvette—particularly when the test sample is a fluid or fluid-like substance. As a result, at least a portion of the cuvette must be at least somewhat transparent for the wavelengths included in the light signal used to interrogate the sample (i.e., the interrogation signal).
For a variety of reasons, it is often desirable to use a low-intensity interrogation signal. To enable an output signal with high signal-to-noise ratio, therefore, materials used in prior-art cuvettes are normally low-refractive-index materials, such as glasses, plastics, calcium fluoride, and the like, which mitigates the amount of optical energy lost in transiting the cuvette itself.
Unfortunately, such materials can be inappropriate for use with some test samples, due to interaction between the cuvette material and the test sample, chemical incompatibility, etc. For more exotic materials, such as calcium fluoride, material cost becomes a significant disadvantage in some applications.
Furthermore, many optical analysis techniques are preferably performed using interrogation signals having wavelengths for which typical cuvette materials are not suitable. Mid-infrared spectroscopy, for example, employs interrogation signals having wavelengths within the range of 2 microns to 15 microns, over which the transmissivity of common cuvette materials is poor.
The need for a cuvette comprising common, low-cost materials that can be configured to have high transmissivity for the spectral content of any of a wide range of interrogation signals remains, as yet, unmet in the prior art.